Acoustic wave filters such as Surface Acoustic Wave (SAW) devices have been used as filters and duplexers installed in communication devices such as mobile phones. The acoustic wave filter is required to have a high degree of suppression in the suppression band and low-loss in the passband. Japanese Patent Application Publication No. 2010-233267 discloses an acoustic wave filter having a Double Mode SAW filter (DMS) and a one-port resonator interconnected. Japanese Patent Application Publication No. 2005-318307 discloses a technique that mounts a chip including a SAW filter on a package. Japanese Patent Application Publication No. 9-326447 discloses a technique that seals an IDT (Interdigital Transducer: comb-shaped electrode) included in a SAW filter by a resin. Japanese Patent Application Publication No. 2010-157956 discloses a technique that provides a top plate made of a metal above an IDT.
The acoustic wave filter has been required to be downsized. When ceilings above IDTs are integrated, the acoustic wave filter can be downsized. However, there may be a case that ceilings are provided above respective IDTs to prevent short between the ceilings. For example, the ceiling may be grounded through an inductor to improve frequency characteristics of the acoustic wave filter. The ceilings are required to have different electric potentials at this time, and in this case, the acoustic wave filter is difficult to be downsized.